Respiratory mucous glycoprotein (MGP) is secreted in a variety of acute and chronic inflammatory processes. How MGP is cleared from the airways is poorly understood. Respiratory mucous glycoprotein was produced in vitro by airways in culture and purified by sizing chromatography, ion exchange chromatography and isoelectric focusing. The effect of free oxygen radicals on MGP was studied by the generation of hydrogen peroxide or the addition of hydrogen peroxide to the purified MGP followed by repeat chromatographic studies by sizing chromatography or HPLC. Oxygen radicals appear to be capable of degrading respiratory MGP to smaller units. The significance or this work lies in the understanding of abnormalities of MGP clearance from airways of patients with acute airway inflammation.